Super-charged NK cells inhibit growth and progression of stem-like/poorly differentiated oral tumorsin vivoin humanized BLT mice; effect on tumor differentiation and response to chemotherapeutic drugs

Abstract

Therapeutic role of NK cells in solid tumors was challenged previously even though their role in hematological malignancies has clearly been established. Furthermore, functions and numbers of NK cells are greatly suppressed in oral cancer patients necessitating effective future NK immunotherapeutic strategies to aid in the control of disease. The humanized-BLT (hu-BLT) mice were used to implant stem-like/undifferentiated oral tumors to study the role of super-charged NK cells with and without feeding with AJ2 probiotic bacteria. Implanted CSC/undifferentiated tumors resected from NK-injected mice exhibited differentiated phenotype, grew slowly, and did not cause weight loss, whereas those from tumor-bearing mice without NK-injection remained relatively more stem-like/poorly-differentiated, grew faster, and caused significant weight loss. Moreover, NK-differentiated tumors were sensitive to chemotherapeutic drugs, and when implanted in the oral-cavity grew no or very small tumors in mice. When NK-mediated differentiation of tumors was blocked by IFN-γ and TNF-α antibodies before implantation, tumors grew rapidly, remained stem-like/poorly-differentiated and became resistant to chemotherapeutic drugs. Loss of NK cytotoxicity and decreased IFN-γ secretion in tumor-bearing mice in PBMCs, splenocytes, bone marrow derived immune cells and enriched NK cells was restored by the injection of super-charged NK cells with or without feeding with AJ2. Much greater infiltration of CD45 and T cells were observed in tumors resected from the mice, along with the restored secretion of IFN-γ from purified T cells from splenocytes in NK-injected tumor-bearing mice fed with AJ2 probiotic bacteria. Thus, super-charged NK cells prevent tumor growth by restoring effector function resulting in differentiation of CSCs/undifferentiated-tumors in hu-BLT mice.

Probiotic-Treated Super-Charged NK Cells Efficiently Clear Poorly Differentiated Pancreatic Tumors in Hu-BLT Mice

“…In contrast, higher expression of CD44 on the tumor cells [20] and increased PD-1 expression in the peripheral blood of patients [19] was correlated with poor tumor differentiation and the aggressiveness of the tumors. In agreement, we have previously shown that increased MHC-class I, CD54, and PD-L1 expression on tumors is correlated with well-differentiated tumors and better prognosis in our in vitro and in vivo studies [22,23].…”

“…Similar to those seen with the pancreatic tumors, implantation of oral stem-like tumors in the oral cavity of hu-BLT mice resulted in similar profiles of cytotoxicity and secretion of IFN-γ from PBMCs isolated from oral tumor bearing mice in the presence and absence of NK injection (23).…”

“…The first dose of AJ2 was given one or two weeks before tumor implantation, and feeding was continued throughout the experiment at an interval of every 48 h. Mice were euthanized when signs of morbidity were evident. Pancreas, pancreatic tumors, bone marrow, spleen, and peripheral blood were harvested and single cell suspensions were prepared from each tissue as described previously [23] and below.…”

“…NK cells and T cells from hu-BLT splenocytes were obtained as described previously by using the human CD56+ and CD3+ selection kits respectively (Stem Cells Technologies, Vancouver, BC, Canada). Monocytes from hu-BLT bone marrow were isolated using human CD14 isolation kit (eBioscience, San Diego, CA, USA) [23].…”

New avenues for melanoma immunotherapy: Natural Killer cells?

“…124 On the other hand, adoptive transfer of NK cells can eliminate the cancer stem cell compartment making the tumour more differentiated and sensitive to chemotherapeutic drugs. 125,126 With regards to innovative therapies, proteasome inhibition, which reduces MHC class I molecules expression, have been shown to upregulate MICA/B and death receptors on several solid tumour CSCs, enhancing NK cell-mediated killing and tumour regression in vivo after NK cell adoptive transfer. 127 Another field of active research is the development of mAbs specifically targeting CSC surface markers.…”